Agreed! The fabric of space-time is variable. It could have been made more clear that could account for inefficiency of the engines. I think there may have been an episode or two in Voyager that stated this, but weren't they mostly cruising at Warp 6 or 7 most of the show because the ship couldn't go past Warp 8 all the time? So this could account for some of the 70 year trip. Another thing is that they couldn't always go in a straight line to the Alpha quadrant, let alone straight to Earth. There are bound to be detours, not to mention that the galaxy is 3 dimensional. Sometimes, they had to travel up and down the Z axis of the galaxy, not just the vector straight to earth, right? That is bound to add years, too.
Ideally, it would be a case that most ships could safely cruise at Warp 6 indefinitely, but cruise at higher warp speeds for correspondingly shorter and shorter periods of time due to the strain on both engines and spaceframe. Non-canon sources would have a ship's maximum warp reserved for relatively short emergency flights of up to twelve hours or so. But as with most things in Trek, there was never a set rule in regard to warp travel times and distances, although VOY did try more than other shows to keep some consistency to where the ship was in relation to home (in light-years) during its journeys.
Someone on this board (don't remember who, unfortunately) likened the label of Warp 10 as analogous to counting to infinity. We have the name and general concept of it, but actually counting to it can't be done because the scale keeps going up and up. You can always change labels and goalposts for new achievements in warp drive, but the concept of omnipresence via warp would remain the same and unreachable. Thus it would seem that Transwarp/slipstream drive < Warp 10, only because Warp 10 is a concept and not an actual measure of speed, whereas transwarp/slipstream and I suppose even time travel can be measured. Things like Warp 13 are not concepts, but measures of speed -- less than omnipresence, but perhaps a more practical term. So to avoid confusion, the label and concept of Warp 10 should probably get a new name.
^^Big problem with that is, we're told Voyager has a "sustainable cruise velocity of warp 9.975" when we first see the ship docked at DS9. That's not even maximum warp, but a cruise velocity they can supposedly maintain. I guess the writers either forgot or decided it was way too fast, since the fastest they ever actually go is warp 9.75 (not 9.975) in "The Swarm"
"Sustainable cruise velocity" is really such an ambiguous term, because it could easily mean the highest speed the ship can sustain for any length of time--be it twelve days, twelve hours, or even just twelve minutes for all we know. I think the easiest way is to refer to Warp 9.975 as being the ship's maximum warp, with higher speeds briefly possible but at extreme risk as was the case once with the Enterprise-D.
If we're going on a large enough scale, there's a big difference between Warp 9.975 and, say, Warp 9.9975, even if seems miniscule on paper because we're adding only .0225. For example, assuming that Voyager maintained Warp 9.975, it would have a speed of 5551.9 times c*. But adjusting it slightly to Warp 9.9975 almost triples the ship's speed, or 14781.9 times c In essence, if a ship even went to Warp 9.999999999, that's still an infinitesimal way to go before "attaining" the omnipresence of Warp 10. And I'm sure there's math out there that the E-D in "Where No One Has Gone Before" reached Warp 9.9999(-to whatever decimal point) to travel 3 million light years (M33) in 10 seconds, which is one of the reasons why dialog of speed was so vague ("We never went past Warp 1.5" or "We're passing [as opposed to reaching] Warp 10" or "We are off the scale"). We do know, however, that whatever Warp 13 or Transwarp is, it's not omnipresence. *using ditl.org's warp speed calculator. I use it not for accuracy or canon evidence (because there is none, really -- as was pointed out earlier, warp is not portrayed consistently), but to demonstrate what speed would look like on an upward, always increasing scale. Funnily enough, ditl.org's warp scale only goes up to 4 decimal points, so it stops displaying calculations between 30 years of warp and 3 years of warp to traverse 3 million ly, which is still a lot of speed used for time saved.
It could be that there's just some kinda bad juju about going Warp 10. It might be that going Warp 9.9999999999999 is safe, and going Warp 13 is safe, but if you go Warp 10, you turn into a lizard and occupy every point in the universe simultaneously. That would explain why starships are often seen going faster than Warp 10 without lizardification happening to the crew. Warp 10 is simply the "brown note" of space travel. EDIT to add: I can manifest the same phenomenon in my 1993 Isuzu Wizard as what happens with the Warp 10 'brown note.' At speeds below 65 MPH, the truck runs fine. But between 65 and 70 MPH, the truck bucks and shudders and makes burning smells. However, once above 70 MPH, it runs well again.
TOS & TAS used a different warp scale, where WF^3 X Chi factor X C = velocity in multiples of C. TNG+ used a table with asymptotes that worked out to roughly WF^3.3 X C, no Chi Factor. AGT apparently revamped the warp scale again. But Roddenberry was dead by that time, and the "No warp 10" thing was his rule. The new scale was a bad idea, IMO; they should have just capped it at 20 old-scale. WNMHGB didn't make it seem effortless and quick, IMO. Now, TFF and TMoMT did make the trip to the core in no time, and encountered two entirely different things in the same place. Can't really argue this once we've cleared up the few discrepancies that can be resolved.
It also means that the original ENT could travel the entire width of the Milky Way in 50-60 days, making our Galaxy far too small for the purposes of the "expanded" show. Really the 60s show made warp too fast, Voyager got it right. I once in a sadder moment used the chart in the Encyclopedia to work out how fast voyager would actually be going to do the journey in 75 years, an average of Warp 5 or 6 - which actually makes sense. If we imagine Stotti is bragging a bit, and take into account what other posters have said, then warp 9.975 is Voyager's equivalent of the Ent-D's Warp 9.6, they can keep it up for a while but then they have to stop or blow up. Also it is on screen in TNG that hammering around damages the engines (The Chase). So Voyager could realistically at "maximum" average around Warp 5 to 6 on it's way home, this also ties in with travel times in general in TNG and DS9. The newer shows and movies fudge this a bit, but you actually have to take things very literally to assume Earth-Kronos take "minutes", assuming a bit of time compression it certainly didn't take long, at most an hour or so, but we can safely assume that nu-trek does it's own thing!
In nuTrek, planets and inanimate objects are thousands of times bigger than in the Prime Universe, as evidenced by the behemoth size of all spacecraft and space stations we've ever seen. Therefore, the space between planets is smaller. Accordingly, travel time to all points in the universe is reduced exponentially. At least, that's my attempt at rationalizing the sewage that is JJ Trek.
Me too. Of course if it were like that, then Tom Paris would be considered a serious pervert. Still... sounds good!